ABSTRACT
We report on the design and fabrication of an Er(3+):Yb(3+) triple clad fiber and on the power scaling of a single frequency fiber amplifier at 1.5 µm based on that fiber. In addition, we report on mode content measurements in order to reveal the overlap of the amplifier output with the TEM(00) mode. The triple clad design was used to enable high output power levels, a good slope efficiency and an excellent beam quality. A maximum single frequency output power of 61 W at 1.5 µm could be achieved with the aid of the co-seeding method, which was used to suppress parasitic processes at 1.0 µm. With a scanning ring cavity the mode content of the amplifier output was analyzed with respect to the TEM modes. For all output power levels the TEM(00) content was above 90%.
ABSTRACT
The performance of a diode-pumped Cr:LiSAF laser and its intracavity frequency-doubled operation is reported. Close to 1 W of quasi-cw power at 870 nm was obtained in multimode operation. Power in excess of 20-mW cw of TEM(00) second-harmonic power at 435 nm has also been obtained by using a lithium triborate crystal with an infrared-to-visible conversion efficiency of 33%. This result is believed to be the highest yet reported for a true cw blue output from a diode-pumped Cr:LiSAF system. However, the maximum attainable output power was limited by thermal fluorescence quenching. The effect of the pump size on the temperature rise and on the small-signal gain is investigated.
ABSTRACT
Photobleaching of darkened thulium-doped ZBLAN fibers is observed after short exposure to visible light. The bleaching process is characterized by a stretched-exponential function of time with an exponent beta independent of both the bleaching intensity and the thulium concentration. The bleaching rate 1/ is also shown to scale linearly with the bleaching intensity and to have a 1/3 -power dependence on the thulium concentration. Incomplete and slow recovery of the color centers is observed in previously bleached fibers, suggesting the presence of at least two types of defect.
